Electric alarm system



1941. o. L-HQEKMAN ETAL 2,249,891

ELECTRIC ALARM SYSTEM Filed Jan. 8, '1938 2 Sheets-Sheet 1 July 22,1941. EKMAN AL 2,249,891

ELECTRIC ALARM SYSTEM Filed Jan. 8, 1938 2 Sheets-Sheet 2 Patented July22, 1941 UNITED STATES PATENT OFFICE ELECTRIC ALARM SYSTEM SwedenApplication January 8, 1938, Serial No. 184,100 In Sweden January 9,193'? 11 Claims.

This invention relates to automatic electric systems for giving thealarm in cases of fire or other danger.

The chief object of this invention is to increase the certainty ofoperation of such systems and to cause the system to operate the alarmeven under unfavourable conditions. Another object of this invention isto render it possible for the system to operate properly, even if a partor parts of the source of electric current are out of operation.

Another object of this invention is to increase the safety against falsealarm.

Other objects will be evident Iro'm the following specification andclaims.

Several embodiments of the invention are ill'u's trated in the annexeddrawings, which "show conheat-ion diagrams or various systems accordingto the invention.

Referring now to Fi 1 of the drawings, ('1 and '17 indicate twoconductors or Wires of a section or control circuit, extending throughthe localities to be protected. Into the wires double current breakersor th'erinocontacts (fusible contacts) F are inserted and arranged at"convenient plates at said localities. The bewire or branch has one endconnected to the plus pole of the battery B via the Winding of a sectionrel-ay Rb, while the other end of said wire is directly connected withthe middle or zero point of the bat- 't'ery. To the same middle pointalso the a-wire is connected through the winding of a section relay Ra,While the other end of the 'a-wire is connected with the minus pole ofthe battery via a small protective resistance Both relays Ra, Rb arenormally supplied with current and are excited, holding their armaturesattracted.

In Fig. 1,as well as in the other fi-gures,-one single section or loopis shown, but other sections may be provided which would preferably beconnected wit-h the battery B in quite similar manner. The number ofsections is arbitrary. "The sections may have three or more wires each.In additibn to the devices shown also indicating members, switches andthe like should be provided, for instance, as shown in U. S. Patent No.2,059,510. Such members do not form any part of this invention and arewel-l 'known in the art. For this reason they are not shown in thepresent drawings.

The system described operates as follows:

When the ii-wire is broken, the currenthormally flowing through therelay Ra is out (iii and f'Ol this reason this relay is lie-energized,falls off and indicates the break in We1l-kn0wn man'- ner. In similarmanner, the relay Rb is de-energized, when the b-wire is broken, andindicates the fault. If both wires are broken simultaneously, the tworelays Ra, Rb are tie-energized at the same time, one or more relays anda fire alarm relay are energized in well-known manner, see for instance,U. S. Patent No. 2,059,510.

In 'case of a short-circuit between the wires 11, b, the relay Ra isevidently short-circuit'ed, independently of the position of the faultwithin the section, because the resistance "of the wires always is verylow in relation to the resistance of the winding of the relay. The relayRa thus short-circuit'ed is lie-energized, falls off and indicates thefault, but the relay Rb has still its full normal. current and remainsexcited, thus preventing false alarm. As shown in Fig. 1, the

middle point of the battery may be permanently grounded. In this case,if a point of the a-Wireis grounded, the relay Ra is short-circuited insimilar manner and 'de en'ergized. If a point of the b 'w-ire isconnected with the earth, nothing happens, such ground connection beingof no importance and having no influence upon the "operation of thesystem.

To attain an equal discharge of the two halves of the battery, theresistance of the relay Rb is, preferably, equal to the sum of theresistances of the protector member m and of the relay Ra. If thewindings of the relays have the same reistance, an equal discharge maybe attained by connecting the conductor it to another inner point of thebattery than the middle point. The protective resistance m, for whichother currentlirniti'ng means may be substituted, may also be arrangedin the conductor H1 or between the central battery connection of theb-wire and the conductor l0.

It is evident that the wires (1, b of the section or sections areconnected with more than two taps of the battery in such manner that ata contact between the wires a potential is carried from one wire to theother at the point of contact, while simultaneously at least one relayof a section remains energized. It is also evident that this result isattained without the use of balance or compensation resistancesconnected in series between the wires. In the systems heretofore knownsuch energy-consuming resistances are necessary which areshort-circuited or cut off in case of contact between the wires.

(Jonsequently, in the systems embodying the present invention, falsealarm is avoided in case of contact between the wires, andsimultaneously a reliable indication of the contact is attained withoutthe use of high, energy-consuming resistances, which reduce thesensitivity of the relays and consequently decrease the safety ofoperation.

The invention may be said to be based upon the following principles:

(1) A short-circuit or contact between the wires a, b shall bring abouta change of the electric state of the section, thus rendering itpossible to effect an indication of the contact.

(2) This change of the electric state must not render all wires of thesame section currentless, because otherwise all section relays will bedeenergized and cause false alarm.

(3) At the point of contact a potential or voltage shall be carried overfrom one wire to the other, to eflect said change of the electric state.

(4) This carrying over of a potential is effected by connecting thewires of the section to separate parts of the same battery or todifferent batteries connected in series, that is, by connecting thewires to at least three taps having different'voltages. Simultaneously,in case of contact, no energy-consuming resistances will beshort-circuited or cut oil. In other words: In the ordinary operation ofthe system no balance or compensation resistances are included in thewires. Such resistances consume considerable quantities of energy andconsequently reduce the sensitivity of the relays, because the energyremaining for the actuation of the relays is reduced by suchconsumption.

When three taps from the battery are used all wires or conductors of thesame section have, preferably, one end connected with one and the sametap of the battery, or with adjacent taps, that is, taps havingsubstantially the same voltage. The other ends of the wires areunsymmetrically connected with other taps each having a substantiallydifferent voltage, in such manner that in case of contact between thewires of the same section at least one relay of the-section will stillhave substantially itsnormal current and hold its armature attracted inan unchanged position. Simultaneously at least one other relay of thesection will be subjected to such a great change of its current that itsarmature changes its position of attraction.

In accordance with this invention small protective resistances, or othermeans for limiting the current may be used, for preventing ashortcircuiting of the battery in case of contact between the wires ofthe section. But such pro tective resistance is here evidently subjectedat most to a part of the voltage of the battery, and, in contrast to thecompensating or balancing resistances heretofore used, such protectiveresistance has not the purpose of preventing false alarm in case ofcontact between the wires of a section.- For these reasons, theprotective resistance may be small and consequently the losses of energytherein are low. Thus, the remaining-energy at disposal for actuatingthe relays is not substantially reduced and the relays will operate moresafely. Consequently, the safety of operation is increased, without anyreduction of the selectivity of the system.

The protective resistance may, for instance, be

7% or /1 of the resistance of the section relay inserted into the samewire.

In the embodiment shown in Fig. 2 the w-wire, from the relay Ra, isplaced first along that part of the bwire, which is next to the relayRb.

The battery B consists of two portions connected in series and havingdifferent voltages. That is, the conductor I0 is connected to anotherpoint than the middle point of the battery. In other respects, thisembodiment is similar to that shown in Fig. 1 and operates in ananalogous manner.

Fig. 3 shows that the protective resistance m. may be placed in theconductor I 0 leading to the central tap of the battery. The source ofcurrent B consists of two distinct batteries, connected in series. Inother respects, this embodiment is analogous with those illustrated inFigs. 1 and 2 and operates similarly.

In the system illustrated in Fig. 4 the a-wire is connected between thetwo outer poles of the battery, that is between the plus pole and theminus pole, and this wire has its section relay Ra at the minus pole.The b-wire is connected with the plus pole via the section relay Rb,while the other end of said Wire is connected with an inner point of thebattery via the conductor H], into which the protective resistance m isinserted. In this case each of the section relays is placed next to anouter pole.

If one or two wires are broken, this system operates in the same manneras that shown in Fig. 1. In case of contact between the wires (1., b,the relay Ra still remains in connection with the plus pole of thebattery and retains its full normal current, if the resistance in issubstantially higher than the resistance of the wire a itself. This istrue in all ordinary systems, because the resistance of the wires 11., bis generally very low. In spite of the condition just mentioned theresistance m may have a very small resistance compared with those of therelays and will consequently consume very little energy.

Thus, in spite of a contact between the wires a, b, the relay Ra remainsunaltered in an energized state and holds its relay attracted. But therelay Rb is short-circuited by that part of the a-wire which is betweenthe plus pole and the point of contact. Thus, Rb is de-energized, lightsits signal lamp and indicates the fault while Ra remains energized andprevents false alarm.

It is evident that the resistor m may be inserted at that end of thea-wire or b-wire which is next to the plus pole.

In the system shown in Fig. 5 the two section relays Ra and Rb are nextto one and the same pole. In the embodiment shown that pole is the pluspole. The resistor m is in the a-wire neXt to the minus pole, but mayalso be placed in the conductor N], that is, in the b-wire.

In case of breaks in one or two wires this system operates just as thesystems shown in Figs. 1-4. In case of contact between the wires a, binFig. 5, the relay Ra will received voltage only from that part of thebattery B which is between the plus pole and the inner point to whichthe conductor i0 is connected. As a result of the voltage thus reducedon the relay Ra said relay is entirely or partially de-energized andfalls off entirely or by one stop, because the resistance of the b-wireis small in relation to that of the resistor m. In order for the relayRa to fall off stepwise, it must evidently be a two or multiple steprelay, see United States Patent No. 2,059,510.

The relay Rb still has its normal voltage and remains in its normalenergized position, preventing false alarm.

From the facts given above it is evident that in the embodiment shown,that is, double-wire sections connected to three different points of thebattery, one end of both wires a, b is connected to a common point ofthe source of current B or to points of that source having substantiallythe same voltage, while the opposite ends of the wires are connectedwith different points of the source, that is with points havingsubstantially different voltages. The system is not symmetrical. In thisway the result is attained that at direct contact or leakage between thewires one relay remains substantially unchanged, that is, retains itsfull normal current and holds its armature in the normal attractedposition, while the other relay is subjected to a substantial change ofVoltage, that is, an increase or decrease, in such manner that itsarmature changes its position of attraction. In other Words its armaturefalls off or is moved to another position. Thus, the fault is indicated.and simultaneously false alarm is prevented. The same is obviously truefor sections having three or more wires.

The section relays Ra, Rb may be placed in one or the other end of thesection. Thus, several combinations are possible. In addition, theindividual sections of a system may be connected in accordance with thedifierent diagrams of connections shown or in accordance with thevarious combinations just mentioned. The position of the protectiveresistor m, for which one or more other current-limiting means, such asfuses, may be substituted, should obviously be chosen with regard to theposition of the relays in the sections and wires. It is to be observedthat in all embodiments, as shown, one and only one of all ends of thewires is directly connected to one and the same tap of the battery,without any relay or other resistance being inserted in that end of thewire.

The winding Ra, Rb may be united to a single two-step relay, as shown inUnited States Patent No. 2,059,510. Similarly, multiple-step relays maybe used for multiple-wire sections. If the source of current or parts ofbattery connected in series have the same voltage, a diiference ofvoltage may be attained by inserting one or more resistors.

Finally, it must be mentioned that the systems as shown are lesssensitive to battery faults than the systems heretofore known. If, inthe systems in accordance with thisinvention, the battery is partiallyput out of operation, for instance, due to the melting of a fuse, thesystem will nevertheless be able to operate by means of the part of thebattery which is still intact, so thatalso in this case alarm will beproperly given in case of danger. If, for instance, in Fig. 4

the right-hand part of the battery is put out of operation, the relay Rawill. fall off to indicate the fault, but the relay Rb still has itsfull normal current from the left-hand part of the battery and will givealarm, if and when relay Rb falls on. On the other hand, the relay Rbprevents false alarm in the case just mentioned, that is, if a fuse atthe plus pole of the battery is burnt out.

In the systems heretofore known the whole system will be put out ofoperation in case of a burnt fuse or other faults in the battery andcannot be operated again, until the fault has been removed or a reservebattery has been put in.

The resistor m may be replaced by a fuse of very low resistance. In thiscase, the section relays are, preferably, slow-acting. If that fusemelts, one of the section relays loses its current and falls off, whilethe other relay has its normal current and is still connected across apart of the battery or across the whole battery, depending upon theposition of the fuse. In contrast to the systems heretofore known thesystem in accordance with the present invention is not put out ofoperation when such fuse is burnt out but may still safely give firealarm.

When it is said above that in certain cases the resistor 112 should berelatively great in relation to the resistance of a wire of a section,this applies only to the case that one of the section relays shallretain its full normal current also after short circuiting or leakage,that is contact between the wires. But if a certain reduction of thecurrent is permitted in that relay which after such contact between thewires remains energized to prevent false alarm, the resistance m needonly be chosen so high that it limits the short-circuiting current ofone half of the battery, to a permissible value. In such case theresistance m may be low in relation to the resistance of a wire.

Reference is made to the copending application of H. T. Nicou, Ser. No.184,892, for Automatic alarm systems, filed January 13, 1938, in whichsystems of a generally similar character as the present are claimed.

What we claim is:

1. In an electric alarm system, in combination,

a source of current having at least three taps of different voltages, aloop of normally closed protective insulated conductors connected tosaid taps, a current breaker connected in each of said conductors andresponsive to the cause of danger for which alarm is to be operated, andan alarm apparatus electrically connected with said loop to be actuatedwhen all the conductors of said loop are broken, only one singleconductor end of a loop being connected with each tap directly, theconductors being connected across different parts of said source.

2. An electric alarm system, comprising, in combination, at least threetaps of different voltages from a source of current, a loop of aplurality of protective wires, a current breaker in each of said wiresand responsive to the cause of danger for which alarm is to be operated,and an alarm apparatus electrically connected with said loop to beactuated when all the wires of said loop are broken, each wire of saidloop having one of its ends connected with one of said taps, while theopposite ends of said wires are connected unsymmetrically with othertaps having other voltages.

3. An electric alarm system, comprising, in combination, a source ofcurrent having at least three taps of different voltages, a protectiveloop of multiple wires connected with said taps and extending throughthe localities to be controlled, circuit breakers connected in saidwires and re-' sponsive to the cause of danger to be controlled, relaysin thewires of said loop, and an alarm apparatus electrically connectedwith said relays to be actuated when all said relays are at leastpartially de-energized, the relay in one wire being next to one pole ofthe source of current, while the other end of said wire is connectedwith a tap from an inner point of said source of current, and said innerpoint being also connected with one end of another wire and its relay,while the opposite end of said other wire is connected with the oppositepole of the source of current.

4. An electric alarm system, comprising a three-tap source of current, amultiple-wire loop extending through the localities to be protected,circuit breakers connected in said wires responsive to the cause ofdanger for which alarm is to be given, one wire of said loop beingconnected across the whole source of cLu'rent, while another wire ofsaid loop is connected with an inner tap of said source of current andwith an outer'tap of said source of current, and relays at the ends ofsaid wires that are connected with said outer taps.

5. An electric alarm system, comprising, in combination, a source ofcurrent having at least threetaps of different voltages, a loop of aplurality of protective normally closed wires extendingthrough thelocalities to beprotected, a circuit breaker connected in each of saidwires and responsive to the cause of danger for which alarm is to begiven, relays connected in the Wires of said loop and to different'outerpole taps of said source of current, and an alarm apparatus electricallyconnected with said loop to be actuated when the wires of said loop arebroken and the relays of said section are at least partiallyde-energized, the ends of said wires remote from said relays beingconnected with said source of current, one with a tap at an intermediatepoint of said source of current and the other with an outer pole tapthereof, opposite to the tap to which the loop relay in the same wire isconnected.

6. An electric alarm system, comprising, in combination, a source ofcurrent having at least three taps of different voltages, amultiple-wire protective, normally closed loop connected with said tapsand extending through the localities to be controlled, circuit breakersin said wires responsive to the cause of danger to be controlled, relaysconnected in the wires of said section at the same outer pole of saidsource of current, an alarm apparatus electrically connected with saidrelays to be actuated when all of said relays are at least partiallyde-energized, the ends of said wires most remote from said relays beingconnected one with an intermediate tap of said source of current and theother with that outer pole of said source of current which is oppositeto the pole to which the relay in the same wire is connected.

7. In an electric alarm system, in combination, a source of directcurrent having at least three taps of different voltages, insulated,protective, normally closed wires connected to said taps to form a loopplaced in the locality to be protected, a circuit breaker connected ineach of said wires and responsive to the cause of danger for which alarmis to be operated, an alarm apparatus electrically connected with saidloop to be actuated when all Wires of said loop are broken, only onesingle wire end of said loop being connected with each tap directly,while the wires of said loop are connected withsaid taps to lie acrossdif-- ferent parts of the source of current, and a current-limitingmember inserted between one of said taps and the wire and that isdirectly connected therewith.

8. In an electric alarm system, in combination, a source of currenthaving three taps of different voltages, a normally closed protectiveloop of a plurality of wires, relays at one end of each of said wires,and an alarm apparatus operable by said relays, one of said wires beingconnected across the whole source of current, while another wire isconnected across only a part of said source of current.

9. In an electric alarm system. the combination of a source of currenthaving at least three taps of difierent voltages, a normally closedprotective loopof a plurality of wires to be open-circuited by apredetermined condition, in dependence of which alarm is to be raised,said wires being connected to said three taps of said source of current,a relay connected to one end of each of said wires, and an alarmapparatus operable by said relays, one of said Wires having itsrelayconnected end connected with one of the taps of the highest voltageof said source of current, while the end-s of said wires which are mostremote from said relays are connected with taps of different voltages. I

10. In an electric alarm system, the combination of a source of currenthaving at least three taps of different voltages, a normally closedprotective loop of a plurality of wires to be opencircuited upon theoccurrence of a predetermined condition and in dependence of which alarmis to be raised, relays connected to one end of each of said wires, andan alarm apparatus operable by said relays, each of said wires beingconnected with two of said taps and across different parts of saidsource, while to each tap only one single wire end is directly connectedwithout any intermediary relay.

11. In an electric alarm system, in combination, a source of currenthaving three taps of difierent Voltages, a normally closed protectiveloop comprising a plurality of parallel insulated conductors each havinga current breaker therein responsive to the cause of danger for whichalarm is to be operated and each having a relay winding inserted intoone of its ends, the conductors of said loop being connected with saidthree taps of different voltages of said current source so that one ofsaid relay windings is connected to that end of a conductor which isconnected with the tap of the highest voltage, while a difference ofvoltage exists between the ends of the said conductors which are mostremote from said relay windings, and an alarm apparatus electricallyconnected with relay contacts controlled by said relay windings to beactuated when all the conductors of said loop are broken.

OLOF INGEMAR HARALD EKNIAN. HANS 'IEODOR NICOU.

